U.S. patent application number 13/695718 was filed with the patent office on 2013-04-25 for composite insulator.
This patent application is currently assigned to LAPP INSULATORS GMBH. The applicant listed for this patent is Volker Hinrichsen, Jens Seifert. Invention is credited to Volker Hinrichsen, Jens Seifert.
Application Number | 20130101846 13/695718 |
Document ID | / |
Family ID | 44582812 |
Filed Date | 2013-04-25 |
United States Patent
Application |
20130101846 |
Kind Code |
A1 |
Hinrichsen; Volker ; et
al. |
April 25, 2013 |
Composite Insulator
Abstract
Disclosed is a composite insulator (1) having a core (2), in
particular made of a fiber-reinforced duromer, and a protective
layer (8) which surrounds the core (2) and is made in particular of
an insulating elastomer. In some sections, especially on the bottom
side of screens (4), the protective layer (8) specifically includes
particles (7) that influence the field of the insulator (1).
Inventors: |
Hinrichsen; Volker;
(Darmstadt, DE) ; Seifert; Jens; (Wunsiedel,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hinrichsen; Volker
Seifert; Jens |
Darmstadt
Wunsiedel |
|
DE
DE |
|
|
Assignee: |
LAPP INSULATORS GMBH
Wunsiedel
DE
|
Family ID: |
44582812 |
Appl. No.: |
13/695718 |
Filed: |
May 27, 2011 |
PCT Filed: |
May 27, 2011 |
PCT NO: |
PCT/EP2011/002627 |
371 Date: |
January 10, 2013 |
Current U.S.
Class: |
428/389 ;
428/375 |
Current CPC
Class: |
H01B 17/325 20130101;
H01B 17/42 20130101; Y10T 428/2933 20150115; Y10T 428/2958
20150115 |
Class at
Publication: |
428/389 ;
428/375 |
International
Class: |
H01B 17/32 20060101
H01B017/32 |
Foreign Application Data
Date |
Code |
Application Number |
May 28, 2010 |
DE |
10 2010 021 882.0 |
Claims
1. A composite insulator (1) with a core (2), in particular of a
fiber-reinforced thermoset, and with a protective layer (8), in
particular of an insulating elastomer, surrounding this core (2),
characterized in that the protective layer (8) comprises in certain
portions particles (7) influencing the field of the insulator
(1).
2. The composite insulator (1) as claimed in claim 1, characterized
in that the protective layer (8) has a number of sheds (4) to
extend the creepage distance.
3. The composite insulator (1) as claimed in claim 2, characterized
in that the protective layer (8') of a partial number of the sheds
(4) comprises the field-influencing particles (7).
4. The composite insulator (1) as claimed in claim 3, characterized
in that the partial number of sheds (4) are located at the
voltage-carrying end (HV).
5. The composite insulator (1) as claimed in claim 2, characterized
in that the protective layer (8') on the underside of at least a
partial number of the sheds (4) comprises the field-influencing
particles (7).
6. The composite insulator (1) as claimed in claim 5, characterized
in that a disk (10) containing the field-influencing particles (7)
is vulcanized on or molded in on the underside of at least a
partial number of the sheds (4).
7. The composite insulator (1) as claimed in claim 5, characterized
in that the protective layer (8') with field-influencing particles
(7) is applied on the underside of at least a partial number of the
sheds (4).
8. The composite insulator (1) as claimed in claim 6, characterized
in that on the underside the sheds (4) have ribs (12), on which the
disk (10) or the protective layer (8') mixed with field-influencing
particles (7) is applied.
9. The composite insulator (1) as claimed in claim 1, characterized
in that the protective layer (8) is mixed with the
field-influencing particles (7) at least in certain portions along
the core (2).
10. The composite insulator (1) as claimed in claim 2,
characterized in that the sheds (4) and/or the core (2) are
surrounded by an outer protective layer (13) that is free from
field-influencing particles (7).
11. The composite insulator (1) as claimed in claim 1,
characterized in that the protective layer (8) is a silicone
rubber, an ethylene-propylene copolymer (EPDM), an ethylene-vinyl
acetate (EVA) or an epoxy resin, wherein a silicone rubber, EPDM,
EVA or epoxy resin mixed with field-influencing particles (7) is
applied in certain portions.
12. The composite insulator (1) as claimed in claim 1,
characterized in that the field-influencing particles (7) are
applied, vulcanized on, applied with the protective layer (8, 8')
or molded in the region of the dry zones of the insulator (1), in
particular on the undersides of sheds (4).
13. The composite insulator (1) as claimed in claim 1,
characterized in that the field-influencing particles (7) are
resistive or capacitive particles or semiconductor particles, in
particular microvaristors of doped ZnO.
14. The composite insulator (1) as claimed in claim 7,
characterized in that on the underside the sheds (4) have ribs
(12), on which the disk (10) or the protective layer (8') mixed
with field-influencing particles (7) is applied.
15. The composite insulator (1) as claimed in claim 3,
characterized in that the protective layer (8') on the underside of
at least a partial number of the sheds (4) comprises the
field-influencing particles (7).
16. The composite insulator (1) as claimed in claim 15,
characterized in that a disk (10) containing the field-influencing
particles (7) is vulcanized on or molded in on the underside of at
least a partial number of the sheds (4).
17. The composite insulator (1) as claimed in claim 16,
characterized in that on the underside the sheds (4) have ribs
(12), on which the disk (10) or the protective layer (8') mixed
with field-influencing particles (7) is applied.
18. The composite insulator (1) as claimed in claim 15,
characterized in that the protective layer (8') with
field-influencing particles (7) is applied on the underside of at
least a partial number of the sheds (4).
19. The composite insulator (1) as claimed in claim 18,
characterized in that on the underside the sheds (4) have ribs
(12), on which the disk (10) or the protective layer (8') mixed
with field-influencing particles (7) is applied.
Description
[0001] The invention relates to a composite insulator according to
the preamble of patent claim 1. Such a composite insulator
comprises a weight-bearing core, which is produced in particular
from a fiber-reinforced thermoset, such as an epoxy resin or a
vinyl ester. To provide the desired insulating properties and
protection from external influences, in particular caused by the
weather, the core is surrounded by a protective layer, which is
produced in particular from an electrically insulating elastomer
such as a silicone rubber.
[0002] When insulating high electrical voltages, the avoidance of
partial discharges is always a necessity. Such discharges,
resulting for example from local increases in the electric field,
lead to instances of damage in the protective layer, in particular
in the case of composite insulators, as a result of which the
service life is reduced. In the case of composite insulators,
measures to avoid local increases in the electric field are
accordingly of great significance. Known for example as a suitable
measure for high-voltage insulators are shielding electrodes, which
are attached to the voltage-carrying fittings and help to avoid
increases in the electric field there, at the ends of the
fittings.
[0003] A great problem of high-voltage insulators in this respect
is the extremely inhomogeneous distribution of the variation in
voltage along their length. A reason for this is stray capacitances
of the insulator to ground. A further problem is local discharges
on soiled insulators, produced for example by increases in the
electric field where there has been local drying.
[0004] To avoid local increases in the electric field, WO
2009/100904 A1 discloses providing at least certain portions of a
composite insulator with a field control layer, which comprises
field-influencing particles. Such particles have, for example, a
resistive or capacitive effect or are semiconducting, and, as a
result of a non-linear relationship between a corresponding
electrical variable and the voltage, contribute to reducing sudden
changes in voltage along the insulator. Mentioned in particular are
microvaristors of ZnO, which above a threshold voltage display an
abrupt reduction in the electrical resistance.
[0005] The object of the invention is to provide a composite
insulator of the type mentioned at the beginning that is further
improved with regard to the avoidance of local discharges.
[0006] This object is achieved according to the invention by a
composite insulator of the type mentioned at the beginning, the
protective layer comprising specifically in certain portions
particles that influence the field of the insulator.
[0007] The invention is thereby based on the idea of placing the
particles that influence the field along the insulator specifically
at certain portions on the insulator in such a way that discharges
that occur during the service life under the external conditions to
be expected and could lead to instances in which the insulating
protective layer is destroyed are avoided as far as possible. In
this respect, investigations have been carried out on long-rod
composite insulators designed for a voltage of 420 kV. With a
number of sheds totalling 10, the long-rod composite insulators
used had a creepage distance with a length of 3.91 m. The low
number of sheds was deliberately chosen to achieve a greater
breakdown tendency of the insulators in the test.
[0008] In a high-voltage laboratory, the insulators were exposed to
artificial rainfall at an angle of 45.degree. in accordance with
the standard IEC 60060-1. The tests were carried out under
alternating voltage. The artificial rain had a conductivity of
.kappa.=+/-100 .mu.S/cm. The voltage applied was increased in
stages. Resultant partial discharges were visually observed. Under
a voltage of 600 kV, a conventionally produced long-rod composite
insulator, the protective layer of which did not have any
field-influencing particles, was observed to undergo as a result
distinct discharges on the underside of the sheds toward the
high-voltage end of the insulator.
[0009] On the basis of this finding, the invention proceeds from
the model concept that exposure of the insulators to rain causes a
conductive coating to form on the upper side of the sheds and along
the shank. As a consequence, a great voltage drop occurs across a
conventional insulator over the dry underside of the sheds. If the
dielectric strength of the surrounding atmosphere is exceeded due
to the resultant local increase in the electric field, local
discharges occur on the underside of the sheds.
[0010] The invention therefore provides in a preferred
configuration that the field-influencing particles are provided in
the region of the aforementioned dry zones of the insulator, in
particular on the undersides of sheds. For this purpose, the
field-influencing particles are separately applied to certain
portions, vulcanized on, applied with the protective layer, sprayed
on, molded on or molded in. For this purpose, the field-influencing
particles are expediently added to a suitable insulating material,
in particular the material of the protective layer. Subsequently,
this material of the existing protective layer is molded on, bonded
on or vulcanized on. The field-influencing particles may also be
admixed with the protective layer in certain portions during the
production of the insulator. Alternatively, the material mixed with
the field-influencing particles may also be overmolded in the
protective layer during the final shaping of the insulator.
[0011] The protective layer and also the material mixed with the
field-influencing particles is preferably a silicone rubber, an
ethylene-propylene copolymer (EPDM), an ethylene-vinyl acetate
(EVA) or an epoxy resin. Accordingly, a silicone rubber, EPDM, EVA
or epoxy resin mixed with field-influencing particles is applied in
certain portions.
[0012] Resistive or capacitive particles or semiconductor particles
are preferably used as field-influencing particles. Microvaristors
of doped zinc oxide (ZnO) are particularly preferred.
Microvaristors of zinc oxide (ZnO) display a non-linear
current-voltage characteristic. Up to a threshold voltage, zinc
oxide may be regarded as a high-impedance resistance and has an
extremely flat current-voltage characteristic. Above the threshold
voltage, the resistance decreases abruptly; the current-voltage
characteristic abruptly changes its steepness.
[0013] If such field-influencing particles, and in particular
microvaristors, that is to say voltage-dependent resistors, are
applied in certain portions to the insulator or with the protective
layer, a local increase in the voltage or electric field is reduced
as a result of the abruptly increased conductivity above the
threshold voltage, so that the undesired local discharges leading
to instances of destruction are prevented.
[0014] If the composite insulator comprises a number of sheds of
the protective layer to extend the creepage distance, in a
preferred configurational variant the field-influencing particles
are comprised by the sheds or are arranged on the sheds. When the
composite insulator is used in an upright position, the dry zones
associated with great changes in voltage lie on the underside of
the sheds. If the field-influencing particles are added to the
protective layer of the sheds or arranged on the sheds, the
discharges undesirably occurring there are avoided. In the case of
this configurational variant, it has been found that not all of the
sheds have to comprise the field-influencing particles. Rather, it
is advantageous if only a partial number of the sheds are provided
with the field-influencing particles. This is dependent on the
variation in voltage over the length of the composite insulator. As
investigations have shown, the greatest changes in voltage should
clearly be expected at the sheds that are arranged at the
voltage-carrying end.
[0015] In a preferred configuration, to this extent the partial
number of sheds provided with field-influencing particles are
located at the voltage-carrying end. Accordingly, starting from the
voltage-carrying end of the composite insulator, initially a
partial number of the sheds are provided with field-influencing
particles. The sheds which then follow are produced conventionally
without field-influencing particles.
[0016] Alternatively, starting from the voltage-carrying end of the
composite insulator, initially a partial number of the sheds may be
provided with field-influencing particles, and then a partial
number of sheds produced conventionally, and this arrangement can
be repeated over the length of the composite insulator.
[0017] It has also been found that the sheds as such do not have to
be provided as a whole with the field-influencing particles.
Rather, to reduce the voltage drop over the dry zone on the
underside of the sheds, it is sufficient to provide only the
underside of the sheds with field-influencing particles. This is
sufficient to reduce the great changes in voltage between the ends
of the sheds and the core or the shank of the insulator.
[0018] In a first configurational variant in this respect, the
field-influencing particles are comprised by a separate disk, in
particular of the material of the protective layer or of some other
insulating material. After conventional production, known per se,
of the sheds by encapsulation, molding, bonding on, shrinking on or
vulcanizing on, the separate disk is vulcanized or bonded onto the
underside of the sheds intended for it. Alternatively, the
separately produced disk containing the field-influencing particles
may be molded into the sheds during production. Finally, it is also
possible to envelop the sheds provided with the separate disk on
the underside in the protective layer in a concluding production
process, in particular by encapsulation or overmolding.
[0019] According to another configuration of the invention, which
can also be used in a combination, it is preferred for the
protective layer as such with field-influencing particles to be
applied on the underside of the intended sheds. For this purpose,
the material of the protective layer is mixed with the
field-influencing particles. Subsequently, the mixed material is
sprayed, molded or vulcanized onto the underside of the sheds.
[0020] In a further preferred configuration, the sheds of the
composite insulator are provided on the underside with ribs, which
lead to a further lengthening of the creepage distance. The
separate disk or the protective layer mixed with the
field-influencing particles is preferably arranged on these ribs,
as prescribed. On account of the increased surface area as a result
of the ribs, improved bonding between the sheds and the separate
disk or the subsequently applied protective layer mixed with
field-influencing particles is achieved.
[0021] Furthermore, it has been found that, in particular in
combination with sheds provided with field-influencing particles on
the underside, a further improvement in the composite insulator
with regard to the avoidance of local discharges is achieved if the
protective layer is provided with the field-influencing particles
at least in certain portions along the core. In particular, the
core is provided with the protective layer that comprises the
field-influencing particles for a partial portion in the vicinity
of the voltage-carrying end of the composite insulator.
[0022] In a further preferred configuration of the composite
insulator, the sheds and/or the core are surrounded by an outer
protective layer that is free from field-influencing particles.
Such an outer protective layer allows account to be taken, if need
be, of the specific external weathering effects to which the
composite insulator is exposed during its use by choosing a
separate material.
[0023] Exemplary embodiments of the invention are explained in more
detail on the basis of a drawing, in which:
[0024] FIG. 1 shows a long-rod composite insulator according to a
first configurational variant,
[0025] FIG. 2 shows a long-rod composite insulator according to a
second configurational variant,
[0026] FIG. 3 shows a detail of a long-rod composite insulator, the
sheds being provided on the underside with a disk containing
field-influencing particles,
[0027] FIG. 4 shows a detail of a long-rod composite insulator, the
sheds being provided on the underside with a protective layer that
comprises field-influencing particles, and
[0028] FIG. 5 shows a detail of a long-rod composite insulator, the
core of which, as compared with the composite insulator that is
shown in FIG. 4, is additionally provided with a protective layer
that comprises field-influencing particles, and
[0029] FIG. 6 shows a long-rod composite insulator according to
FIG. 5, the sheds including the protective layer mixed with
field-influencing particles being enveloped in an outer protective
layer.
[0030] Represented in FIG. 1 is a long-rod composite insulator 1,
which comprises a core 2 of a glass-fiber-reinforced plastic, on
which ten sheds 4 are arranged, distributed over the length, to
extend the creepage distance. Fastened to the ends of the core 2
are the connection fittings 5, 6. The connection fitting 6 is
intended for the electrical contacting with a high voltage HV, and
to this extent has the voltage-carrying end of the insulator 1.
[0031] The long-rod composite insulator 1 represented, with a total
of ten sheds 4, is designed for the insulation of a voltage of
approximately 400 kV. The core 2 is enveloped throughout in a
protective layer 8 of a silicone rubber. Fastened on this envelope
of the core 2 are the sheds 4. The sheds 4 are also produced from
silicone rubber.
[0032] To avoid local discharges as a result of increases in the
electric field or as a result of great changes in voltage, the
protective layer 8 of the core 2 is mixed with field-influencing
particles 7 over the entire length of the composite insulator 1.
The field-influencing particles 7 are microvaristors of doped ZnO.
Furthermore, at the voltage-carrying end of the composite insulator
1, that is to say adjoining the fitting 6, five of the total of ten
sheds 4 are produced from silicone rubber mixed with
field-influencing particles 7.
[0033] In a rain test, a long-rod composite insulator 1
corresponding to FIG. 1 displays a distinctly reduced discharging
tendency on the underside of the sheds 4 as compared with a
conventional long-rod composite insulator without field-influencing
particles. The reason for this is that the microvaristors of ZnO
become conductive under high voltages, so that the changes in
voltage from the wetted upper side of the sheds 4 to the portion of
the core 2 lying thereunder are reduced distinctly.
[0034] Represented in FIG. 2 is a long-rod composite insulator 1
that is similar in its basic construction to FIG. 1. It differs in
that the protective layer 8 along the core 2 is now not provided
with field-influencing particles 7. Rather, only the five sheds 5
adjacent the voltage-carrying end of the composite insulator 1 are
produced from a protective layer 8 that is mixed with
field-influencing particles.
[0035] In a rain test, this composite insulator 1 according to FIG.
2 also displays a distinctly reduced sparkover tendency on the
underside of the sheds 4 as compared with a conventional long-rod
composite insulator without field-influencing particles 7.
[0036] Represented in FIG. 3 is a partial detail of a long-rod
composite insulator 1 corresponding to FIG. 1 or 2. In this case,
two sheds 4 in the vicinity of the voltage-carrying end, that is to
say in the vicinity of the fitting 6, are shown.
[0037] The long-rod composite insulator 1 corresponding to FIG. 3
comprises the core 2 of a glass-fiber-reinforced plastic. On the
core 2, a protective layer 8 of silicone rubber is applied. Mounted
on this protective layer 8 are the sheds 4.
[0038] To influence the electric field or to reduce great changes
in voltage, a separate disk 10 of prefabricated EPM that contains
field-influencing particles 7 is fastened on the underside of the
sheds 4.
[0039] Corresponding to a first configurational variant, the
separate disk 10 has correspondingly been vulcanized onto the
underside of the upper shed 4. Corresponding to a second
configurational variant, the separate disk 10, containing the
field-influencing particles, is molded into the material of the
shed 4, as can be seen from the lower shed 4.
[0040] According to FIG. 4, the sheds 4 of another variant of the
long-rod composite insulator 1 comprise a number of peripheral ribs
12 on the underside. A protective layer 8' that contains the
field-influencing particles 7 is molded onto these ribs 12.
According to FIG. 5, the long-rod composite insulator 1 has at
least in certain portions on the core 2 a further surrounding
protective layer 8', which in turn is mixed with field-influencing
particles.
[0041] According to FIG. 6, the protective layer 8' with
field-influencing particles that is provided on the underside of
the sheds 4 is molded into the sheds 4. In addition, in particular
according to a concluding production step, the long-rod composite
insulator 1 shown in FIG. 6 is enveloped in an outer protective
layer 13 of silicone rubber that does not comprise
field-influencing particles 7.
DESIGNATIONS
[0042] 1 composite insulator [0043] 2 core [0044] 4 shed [0045] 5
connection fitting [0046] 6 connection fitting [0047] 7
field-influencing particles [0048] 8 protective layer [0049] 8'
protective layer with field-influencing particles [0050] 10 disk
[0051] 12 ribs [0052] 13 outer protective layer [0053] HV
high-voltage end
* * * * *